Errors in Ruby

In the following sentence: The raise method is from the Kernel module.
By default, raise creates an exception of the RuntimeError class. From:
http://rubylearning.com/satishtalim/ruby_exceptions.html

What is meant by raising an exception of the “RunTimeError”? And, if we
raise it on “ArgumentError”, what is mean by that?

Thanks.

On Jul 13, 2010, at 2:07 PM, Abder-rahman Ali wrote:

In the following sentence: The raise method is from the Kernel module.
By default, raise creates an exception of the RuntimeError class. From:
http://rubylearning.com/satishtalim/ruby_exceptions.html

What is meant by raising an exception of the “RunTimeError”? And, if we
raise it on “ArgumentError”, what is mean by that?

irb:0> ArgumentError.ancestors
=> [ArgumentError, StandardError, Exception, Object, Kernel]
irb:0> RuntimeError.ancestors
=> [RuntimeError, StandardError, Exception, Object, Kernel]
irb:0> RuntimeError.superclass
=> StandardError
irb:0> ArgumentError.superclass
=> StandardError
irb:0> begin
irb:1* raise “foo”
irb:1> rescue Exception => e
irb:1> puts e.class
irb:1> end
RuntimeError

Hth, Sandor
Szücs

On 13 Juli, 14:07, Abder-Rahman A. [email protected]
wrote:

In the following sentence: The raise method is from the Kernel module.
By default, raise creates an exception of the RuntimeError class. From:http://rubylearning.com/satishtalim/ruby_exceptions.html

What is meant by raising an exception of the “RunTimeError”? And, if we
raise it on “ArgumentError”, what is mean by that?

Thanks.

Posted viahttp://www.ruby-forum.com/.

Hi,

Exceptions are just regular classes in ruby. You can create your own
or use the multitude of built in Exceptions.

Exception are usually very simple classes. The reason why you might
need more than one is differentiation. Sometimes things can go wrong
in more than one way.

begin

Do stuff that raises an exception

rescue MyFirstException => err
puts “MyFirstException occurred”
rescue MySecondException => err
puts “MySecondException occurred”
end

Usually you can distinguish what an exception is supposed to represent
by its name. RunTimeError is a kind of catch-all error, you can trap
almost every “normal” error using this exception class. An
ArgumentError on the other hand is more specific and is raised when
you try to call methods using the wrong number or type of arguments.

def foo(x, y)
puts x, y
end

foo(3) => raises ArgumentError

/lasso

Lars O. wrote:

On 13 Juli, 14:07, Abder-Rahman A. [email protected]
wrote:

In the following sentence: The raise method is from the Kernel module.
By default, raise creates an exception of the RuntimeError class. From:http://rubylearning.com/satishtalim/ruby_exceptions.html

What is meant by raising an exception of the “RunTimeError”? And, if we
raise it on “ArgumentError”, what is mean by that?

Thanks.

Posted viahttp://www.ruby-forum.com/.

Hi,

Exceptions are just regular classes in ruby. You can create your own
or use the multitude of built in Exceptions.

Exception are usually very simple classes. The reason why you might
need more than one is differentiation. Sometimes things can go wrong
in more than one way.

begin

Do stuff that raises an exception

rescue MyFirstException => err
puts “MyFirstException occurred”
rescue MySecondException => err
puts “MySecondException occurred”
end

Usually you can distinguish what an exception is supposed to represent
by its name. RunTimeError is a kind of catch-all error, you can trap
almost every “normal” error using this exception class. An
ArgumentError on the other hand is more specific and is raised when
you try to call methods using the wrong number or type of arguments.

def foo(x, y)
puts x, y
end

foo(3) => raises ArgumentError

/lasso

Thanks for your reply.

I just want to ask a thing since I’m new to Ruby.

When you say: rescue MyFirstException => err

How do you read this =>

Thanks.

Thanks Sandor.

On 13 Juli, 16:51, Abder-Rahman A. [email protected]
wrote:

Thanks Sandor.

Posted viahttp://www.ruby-forum.com/.

Hi,

The “=> err” is not really needed, it just makes the error object
available as a variable for further use. Like in:

begin
raise “Killer robots!”
rescue Exception => err
puts “#{err.message} (#{err.class})” # prints ‘Killer robots!
(RuntimeError)’
end

/lasso

Thanks a lot Lasso, that makes it clear.

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